Field technicians in a variety of commercial and governmental disciplines travel to multiple sites in different geographic locations in order to audit, repair, replace, or otherwise maintain the systems located at the site. A field technician can be assigned to maintain a number of different sites. Particular equipment may be required at any given site depending on the nature of the problem. If the field technician does not have that particular equipment with him, the field technician often must retrieve it from a warehouse.
The use of the same reference symbols in different drawings indicates similar or identical items.